1. Field of the Invention
The present invention relates to a method of manufacturing a linear-motion device employed in a common industrial machine, a transferring machine, etc.
In particular, the present invention relates to a linear-motion device employed in an XY table unit, or the like, for example.
The present invention also relates to a slider of a linear-motion guide bearing unit in which a configuration of a slider block is improved, and a linear-motion guide bearing unit constituting a linear guide having this slider and employed in a machine tool, an industrial machine, etc.
2. Description of the Related Art
A configuration of the linear-motion guide bearing unit will be explained while taking an example.
The linear-motion guide bearing unit has the guide rail that extends in the axial direction and has an almost square sectional shape, and the slider that is fitted to this guide rail and has a substantially U-shaped sectional shape. The rolling-element rolling grooves are formed on both side surfaces of the guide rail in two columns, four columns, or the like in total in the axial direction.
Also, the slider comprises the slider block and the end caps fitted to both end portions of the slider block in the axial direction. In addition, the side seals for sealing the openings of the clearance between the guide rail and the slider are fitted to both end portions of the slider (end surfaces of respective end caps).
Further, the slider block has the rolling-element rolling grooves, which oppose to the rolling-element rolling grooves of the guide rail, on the inner side surfaces of both sleeve portions, and also has the rolling-element return paths, which pass through the thick positions of the sleeve portions in the axial direction. Then, the rolling-element rolling paths are constructed by both opposing rolling-element rolling grooves
Meanwhile, the end cap has the curved path that communicates the rolling-element rolling path with the rolling-element return path that is formed in parallel with the rolling-element rolling path. The rolling-element circulation paths are constructed by the rolling-element rolling paths, the rolling-element return paths, and the curved paths provided to both ends. A large number of rolling elements made of the steel balls, for example, are charged in the rolling-element circulation paths.
The slider fitted to the guide rail are moved smoothly along the guide rail via rolling operations of the rolling elements in the rolling-element rolling paths. The rolling elements are rolled in the rolling-element circulation paths in the slider during the movement and are infinitely circulated.
In such linear-motion guide bearing unit in the prior art, the rolling elements held in the retainer are charged into the rolling-element circulation paths and then the slider is fitted to the guide rail.
In the linear-motion guide bearing unit, the tongue portion that picks up the rolling elements from the rolling-element rolling path to feed to the curved path is provided in the end cap. In this case, if the linear-motion guide bearing unit is assembled as mentioned above (if the slider is fitted to the guide rail in the situation that the rolling elements have already been charged in the rolling-element circulation paths), the rolling elements are moved in zigzags and thus come into contact with the tongue portion when the rolling elements pass through near the tongue portion, and thus there is a possibility that the tongue portion is subjected to the damage (see FIG. 8).
Also, the above assembling method has a first problem that, when the slider is fitted to the guide rail, the rolling elements are ready to fall off from the slider.
In addition, an appropriate amount of rolling elements must be charged into the rolling-element circulation paths. But it is difficult to check whether or not a charged amount of rolling elements is the appropriate amount.
Further, in case the rolling elements are charged into the rolling-element circulation paths while interposing the spacers between the rolling elements, it is difficult to check whether or not the spacers are interposed between the rolling elements without fail.
On the other hand, normally the linear-motion device employed in the XY table unit, or the like comprises the guide rail, the slider provided onto this guide rail, and a large number of rolling elements used to cause this slider to move relatively in the longitudinal direction of the guide rail. Then, the slider has the slider block having the rolling-element rolling grooves that oppose to the rolling-element rolling grooves formed on the guide rail, and the end caps that close both-end openings of the rolling-element rolling paths formed between the rolling-element rolling grooves on this slider block and the rolling-element rolling grooves on the guide rail. The rolling-element return paths for returning the rolling elements, which have rolled in the rolling-element rolling paths, are formed in parallel with the rolling-element rolling paths.
By the way, in the prior art, if the rolling-element return paths are formed on the slider block of such linear-motion device, the rolling-element rolling grooves are formed on inner side surfaces of the slider block by applying the drawings process to the slider block and then the rolling-element return paths are formed by applying the drilling process to the slider block.
However, if the rolling-element return paths are formed on the slider block according to such method, there is a second problem such that the surface undulation precision of the inside of the rolling-element return paths is bad and the surfaces of the rolling elements that roll in the rolling-element return paths are easily spoiled. Also, according to the above method, it is difficult to form the rolling-element return paths on the slider block by one step. Thus, since at least two steps are needed to form the rolling-element return paths, much cost and time are needed.
Further more, the slider of the linear-motion guide bearing unit, which is fitted to the guide rail that extends linearly, has a plurality of ball circulation paths to extend over the slider block and the end caps coupled to both ends of the slider block respectively. Respective ball circulation paths consist of the rolling-element rolling paths and the rolling-element return paths formed in the end caps in parallel with each other, and the coupling ball rolling portions formed in both end caps to connect both ends of both ball rolling portions. A large number of steel balls that cause the slider to move relatively along the guide rail are charged in the ball circulation paths.
In the prior art, the rolling-element return paths are formed by elongate holes that pass through the slider block. Since a number of balls roll in the through holes, inner surfaces of the through holes must be formed smoothly.
Since the through holes opened in the slider block are elongate, much time and labor to open the through holes are required. Therefore, this third problem acts as one cause of high cost of the slider or the linear-motion guide bearing unit having the slider.